Alton Dooley over at Updates from the VPL has some excellent photos of the holotype material of Agnosphitys cromhallensis from the Upper Triassic fissure fills of England. The name, 'unknown begetter', reflects upon the unclear phylogentic relationships of this taxon. The original describers, Fraser et al. (2002), considered it to be a dinosauromorph more derived than Eoraptor and Herrerasaurus, but just outside of Dinosauria. It is known from an isolated left ilium, a left maxilla, a right humerus and a left astragalus. There is also a referred tooth. The association of this material was questioned with Langer (2004) considering it a nomen dubium.
The ilium possesses a distinct brevis shelf and 'open' ventral portion of the acetabulum (so it was slightly perforated), yet only has scars for two sacrals. The subrectangular deltopectoral crest on the humerus is typical for dinosauromorphs and the astragalus is very similar to that of basal saurischians (Nesbitt et al., 2007). Thus these specimens contain a melange of basal and derived characters making its phylogenetic placement uncertain (Fraser et al., 2002). This is also a very small animal as the humerus length is under 35mm. Unfortunately, more material needs to be found to elucidate the relationships of this animal, but what is present is not only very well preserved but extremely interesting.
Fraser, N. C., Padian, K., Walkden, G. M., and Davis, A. L. M. 2002. Basal dinosauriform remains from Britain and the diagnosis of the Dinosauria. Palaeontology 45:79–95.
Langer, M.C. 2004. Basal Saurischia. In: Weishampel, D.B., Dodson, P., & Osmolska, H. (Eds.). The Dinosauria (2nd Edition). Berkeley: University of California Press. Pp. 25–46.
Nesbitt, S. J., Irmis, R. B. & Parker, W. G. 2007. A critical re-evaluation of the Late Triassic dinosaur taxa of North America. Journal of Systematic Palaeontology 5, 209-243.
Kurt Gödel's Open World
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